This invention relates generally to the field of musical instruments, more particularly to membranes adapted for use in the capacitive electric musical instrument vibration transducers. A membrane is a flexible, acoustically-emitting vibrating surface on an acoustic musical instrument like a drum, banjo, tambourine, or other such instrument. The acoustic properties of a membrane is defined in part by the amount of tension applied to the membrane at its perimeter by an external device. These membranes are often referred to generally as drumheads, but the more general term membrane will be used in this discussion. Membranes in common use at the time of this writing frequently comprise thin plastic sheets, made of materials such as nonconductive polyester, animal hides, or Kevlar, attached to metal rings (sometimes referred to as hoops) at their perimeters. These rings fit over the shell or body of their respective instruments, and tension is applied to the membrane by a metal rim fastened to the instrument shell or body with tension rods. By adjusting the tension in the tension rods, the acoustic properties of the instrument (such as the frequencies of vibration of a drum) can be changed. Other tensioning devices, such as a simple string or rope looping through holes in the membrane and attached to an instrument shell or another membrane, are used as well. Both drums and banjos use nearly identical arrangements for applying tension.
A novel capacitive electric vibration transducer has been described in a related application for creating microphone-like signals describing an acoustic musical instrument's sound. These transducers can provide cleaner signals with better acoustic isolation than microphones, magnetic pickups, or other types of transducers can provide. Drums, banjos, tambourines, and other similar instruments commonly use membranes as their acoustically-emitting vibrating surfaces, and are in many respects ideal candidates for the use of these capacitive electric transducers. Their membranes, however, must include a vibrating variable capacitor plate as part of their construction, as well as a method for providing electrical contact between the vibrating variable capacitor plate and the electrical circuit portion of the transducer.
As part of a pressure transducer triggering device for electronic drum systems, which generate signals through the use of a synthesizer or similar electronic device instead of using an acoustic instrument's vibrations directly, Duncan shows a drumhead-like device consisting of a layer of conductive rubber with an array of 3D projections placed underneath a protective cover layer. This device is not designed to be applied to a traditional acoustic drum or any other acoustic instrument, which requires the adjustable application of tension not present in Duncan's device. Furthermore, this device is not suitable for use with the vibration transducer referenced above because the rubber layer significantly dampens any vibrations in the cover layer (rubber is commonly used as an acoustic damping material). The array of projections in the rubber needed for Duncan's device dampen vibrations even further, making Duncan's device even more unsuitable for use in an acoustic musical instrument. These shortcomings for the present application are understandable because Duncan's invention is not intended to be an acoustic musical instrument either in whole or in part; it is merely a triggering device for synthesizers, drum modules, and the like.
Apart from the capacitive electric musical instrument vibration transducer mentioned above, modern drums and banjos may sometimes have other kinds of electronics placed inside their shell bodies. For example, microphones and triggering devices for synthesizers, drum modules, and other such devices can be incorporated into a traditional acoustic drum. These devices may be susceptible to electromagnetic interference from external electrical devices, such as a computer or a nearby radio transmitter tower, and may benefit from electromagnetic shielding on the instrument. Since membranes can constitute the majority of the surface area of an instrument body for an instrument like a drum or banjo, it can be useful to incorporate electromagnetic shielding into a musical membrane directly, including means of grounding the shielding electrically.
The primary object of this invention is to provide musical membranes (including drumheads and banjo membranes) specially adapted for use with the capacitive electric musical instrument vibration transducers referenced above. These drumheads will include an acoustically-emitting layer, a vibrating variable capacitor plate, and means of electrically connecting the plate to the electrical circuitry of the vibration transducer.
Another object of the invention is to provide musical membranes with integrated electromagnetic interference shielding for other applications. These membranes will include an electrically conducting portion of the membrane suitable for use as shielding, along with an electrical connection used for grounding the shielding electrically to the same potential as other shielding on the musical instrument.
A fuller understanding of the nature of the objects of the present invention will become apparent upon consideration of the following detailed description taken in connection with the accompanying drawings, wherein: